POS0313 INVESTIGATING THE RELATIONSHIP BETWEEN METHOTREXATE ADHERENCE AND BIOLOGIC RESPONSE IN RHEUMATOID ARTHRITIS PATIENTS
Authors: A. B. Mohammad Ariff, N. Nair, J. Bluett, A. Barton, S. Viatte, D. Plant, K. Hyrich, A. G. Wilson, A. Morgan, J. Isaacs
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> In rheumatoid arthritis (RA), methotrexate (MTX) adherence is highly variable and typically suboptimal, with reports of adherence 59% (underuse) to 107% (overuse) [1]. Non-adherence to MTX may explain non-response and the need to start or switch to biologic therapies. Concomitant use of MTX is associated with reduced anti-drug antibodies in patients prescribed biologics such as adalimumab, therefore promoting MTX adherence should be a priority [2]. MTX biochemical adherence can be objectively measured using HPLC-SRM-MS [3] <h3>Objectives</h3> To investigate the biochemical MTX adherence in RA patients commencing a biologic and its association with EULAR response. <h3>Methods</h3> This analysis used data from the Biologics in Rheumatoid Arthritis Genetics and Genomics Study Syndicate (BRAGGSS), a one-year UK prospective cohort study of patients with RA commencing a biological drug. Prior to biologics commencement, demographic and clinical data were collected. Serum samples were sampled for MTX biochemical adherence at baseline (pre-treatment of biologics), then 3 and 6 months post-first dose. MTX concentration was measured by HPLC-SRM-MS. Time to processing variable was also noted by calculating the difference between the time the sample was processed and the time the blood was sampled. Adherence was calculated based on a cut-off limit taken from a validated MTX adherence assay. A chi-square test was used to investigate the association between adherence and biologic response. Linear regression investigated the relationship between MTX level and time to processing. <h3>Results</h3> 582 patients were included; 75% female, mean (S.D.) age 58 (12) years. Table 1 summarises the baseline characteristics for all patients. There was no significant relationship between adherence at pre-treatment with EULAR response at 6 month (p=0.17). However, those who were biochemically adherent to MTX at 6 months had a statistically significantly better response to biologic therapy (p=0.04). It is also found that despite being a responder to the biologic, 37% were non-adherent to MTX. However, there was no significant relationship between MTX level and time to processing thus it is unlikely to be due to the stability of MTX in blood over time. <h3>Conclusion</h3> Patients who were adherent to MTX, assessed biochemically, at 6 months after starting biologic therapy had better response to treatment, which may further strengthens the evidence to support the importance of concomitant use of MTX with biologics. <h3>References</h3> [1]Hope HF, Bluett J, Barton A et al. Psychological factors predict adherence to methotrexate in rheumatoid arthritis; findings from a systematic review of rates, predictors and associations with patient-reported and clinical outcomes. <i>RMDOpen</i> 2016;2:e000171. [2]Krieckaert CL, Nurmohamed MT, Wolbink GJMethotrexate reduces immunogenicity in adalimumab treated rheumatoid arthritis patients in a dose dependent manner. <i>Annals of the Rheumatic Diseases</i> 2012;71:1914-1915. [3]Bluett J, Riba-Garcia I, Verstappen SMM, et al. Development and validation of a methotrexate adherence assay. <i>Annals of the Rheumatic Diseases</i> 2019;78:1192-1197. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Amirah binti Mohammad Ariff: None declared, Nisha Nair: None declared, James Bluett Grant/research support from: Received a research grant award from Pfizer and travel/conference fees from UCB, Pfizer, Fresenius Kabi and Eli Lilly., Anne Barton: None declared, Sebastien Viatte: None declared, Darren Plant: None declared, Kimme Hyrich: None declared, Anthony G Wilson: None declared, Ann Morgan: None declared, John Isaacs: None declared.